Home loan dispute

Without settle the loan amount the title of property can not be  changed. 

Contact the banker.  There is certainly a way out of giving a fresh loan to the son, and then crediting that amount to the old loan of father, and accepting such sale deed from father as fresh loan, if the account is in order and not NPA.

Your father has to first discharge the loan in full, retrieve the title documents from bank along with no due certificate and cancellation of mortgage registration, after which he can transfer the property to his son.